This invention relates to a current control functional device, and in particular, to a functional device which is capable of using as a basic cell of a logic gate or a memory and which utilizes degree of freedom regarding spin of an electric charge carrier.
A limitation with respect to operation speed or integration has been pointed out in a logic gate or a memory which is composed of a silicon bipolar or CMOS (Complementary Metal Oxide Semiconductor). Under this circumstance, it has been expected to realize a new device which utilizes new operation principle exceeding the limitation of the above-mentioned device.
To this end, a new trial has been made about a device which uses degree of freedom of electron spin. A spin injection type transistor has been so far reported in Material Science and Engineering B31, pp. 199-205 (1995) by M. Johnson as the device which utilizes the degree of freedom of the spin.
Further, a memory cell using ferromagnetic substance laminate structure of spin-valve type has been also reported in Japanese journal of Applied Physics 34, L415-417 (1995) by Y. Irie. et al.
Recently, attention has been paid for a single electron transistor (SET) as a device having super low power consumption because it is an extreme electron device which is capable of discriminating each electron. Moreover, suggestion has been made about a single electron-tunneling device having degree of freedom of spin.
However, an output signal is small in either one of the above-mentioned conventional spin injection type transistor or the spin-valve type memory cell. Therefore, a device having a larger output signal has been required to improve device characteristic.
Further, although each of these devices may serve as a memory cell, it is unsuitable for a basic logic device because it does not almost have load-driving capability. Namely, an output signal is small, and is inferior in the load-driving capability in the conventional device which utilizes the spin of the electric charge carrier.
Moreover, an electrode, in which spins are completed in only a third electrode of a center, has been used in the conventional device. In the conventional device, the degree of freedom of the spin is introduced into the single electron tunnel device. In addition, the degree of freedom of the spin is not effectively used in the conventional device because a normal ferromagnetic substance is used as electrode material.